How to Calculate the Absolute Neutrophil Count (ANC)
The ANC is calculated by multiplying the total white blood cell count (WBC) by the sum of the percentages of segmented neutrophils and bands, then dividing by 100.
The Formula
ANC (cells/mm³) = WBC (cells/mm³) × (% segmented neutrophils + % bands) ÷ 100 1, 2
Step-by-Step Calculation
Step 1: Obtain the total WBC count from the complete blood count (typically reported in cells/mm³ or K/µL, where 1 K/µL = 1,000 cells/mm³) 1
Step 2: Obtain the differential percentages for segmented neutrophils (also called "segs" or mature neutrophils) and band neutrophils (immature neutrophils) from the manual differential count 1, 2
Step 3: Add the percentage of segmented neutrophils to the percentage of bands 1
Step 4: Multiply the total WBC by this combined percentage and divide by 100 to get the ANC 3
Practical Example
If a patient has:
- WBC = 8,000 cells/mm³
- Segmented neutrophils = 60%
- Bands = 10%
Then: ANC = 8,000 × (60 + 10) ÷ 100 = 8,000 × 0.70 = 5,600 cells/mm³ 3
Critical Clinical Thresholds
ANC < 500 cells/mm³: Severe neutropenia requiring urgent evaluation and empiric antibiotics if fever is present 4
ANC < 1,000 cells/mm³: Grade 3-4 neutropenia; hold myelosuppressive drugs until ANC ≥ 1,500 cells/mm³ 4
ANC ≥ 1,500 cells/mm³: Generally considered safe threshold for resuming chemotherapy after drug-induced neutropenia 4
Essential Caveats
Manual differential is mandatory for accurate band assessment—automated analyzers cannot reliably distinguish band forms from mature neutrophils, and manual 500-cell differentials provide the most accurate band counts 1, 2, 5
Absolute band count ≥ 1,500 cells/mm³ has the highest diagnostic accuracy (likelihood ratio 14.5) for bacterial infection, making it more clinically significant than the total WBC count alone 1, 2
Left shift (≥16% bands) can occur with completely normal total WBC counts and still indicates significant bacterial infection requiring urgent evaluation 1, 2
When monitoring chemotherapy-induced neutropenia, growth factors can be used in combination with tyrosine kinase inhibitors for patients with resistant neutropenia 4